1. Field of the Invention:
This invention relates to a process for the grafting of ethylene onto a diene polymer, such as polybutadiene, in the presence of a catalyst comprising a titanium or vanadium halide, such as titanium tetrachloride, an aluminum trihydrocarbon, such as aluminum triisobutyl, and a carbonyl or thiocarbonyl compound, such as acetophenone.
2. Related Prior Art:
The grafting of ethylene onto conjugated diene polymers has been reported. However the product is a conglomeration of various polymers including the original or starting diene polymer and homopolymer of the olefin in addition to the grafted copolymer.
For example, Von G. Gerber et al disclose in "Makromolekulare Chemie": 64, 68 (1963) the grafting of ethylene onto butadiene polymers using TiCl.sub.4 and HAlR.sub.2 as the catalyst. The butadiene polymers have pendent vinyl groups to which dialkyl aluminum hydride is attached according to the reaction: ##EQU1## The resultant polymer having the dialkyl aluminum ethyl pendent group is then reacted with ethylene to produce polyethylene blocks. From the several extractions reported with various solvents it is obvious that the reaction product is a mixture of several types of polymers including homopolymers. Because of the variety of products obtained it is difficult to control the type of polymer produced and the removal of undesired homopolymers is necessary. Moreover it appears that this type of grafting requires the presence of pendent vinyl groups such as in 1,2 polybutadiene.